About a year ago, at $70k we had 22.6 trillion difficulty. Currently, at $16k, we have 36 trillion difficulty. Apparently, hash rate isn't mainly affected by the price.
I think it's safe to assume the hash rate would have been much higher now if Bitcoin would have been at $100k now. The fact that it still went up is probably because new mining hardware got more powerful, but miners have much less money to spend.